(19)
(11) EP 1 043 864 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
10.09.2003 Bulletin 2003/37

(43) Date of publication A2:
11.10.2000 Bulletin 2000/41

(21) Application number: 00107473.1

(22) Date of filing: 06.04.2000
(51) International Patent Classification (IPC)7: H04L 9/30, H04L 9/08
(84) Designated Contracting States:
AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE
Designated Extension States:
AL LT LV MK RO SI

(30) Priority: 21.12.1999 US 469726
06.04.1999 US 128164 P

(71) Applicant: ContentGuard Holdings, Inc.
Wilmington, Delaware 19803 (US)

(72) Inventor:
  • Wang, Xin
    Los Angeles, CA 90007 (US)

(74) Representative: Grünecker, Kinkeldey, Stockmair & Schwanhäusser Anwaltssozietät 
Maximilianstrasse 58
80538 München
80538 München (DE)

   


(54) System and method for document distribution


(57) Methods for transferring among key holders in encoding and cryptographic systems the right to decode and decrypt messages in a way that does not explicitly reveal decoding and decrypting keys used and the original messages. Such methods are more secure and more efficient than typical re-encoding and re-encryption schemes, and are useful in developing such applications as document distribution and long-term file protection.






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